Sen. Marco Rubio stands behind a curtain preparing to speak while Iowa State Rep. Bobby Kaufmann presents him to the crowd at the Mediacom Outdoor Club in Kinnick Stadium in Iowa City, Thursday, Dec. 10, 2015. The republican presidential hopeful made a stop in Iowa City for a meet and greet after visiting Des Moines, Iowa, and Ames, Iowa, earlier in the day.

Sen. Marco Rubio stands behind a curtain preparing to speak while Iowa State Rep. Bobby Kaufmann presents him to the crowd at the Mediacom Outdoor Club in Kinnick Stadium in Iowa City, Thursday, Dec. 10, 2015. The republican presidential hopeful made a stop in Iowa City for a meet and greet after visiting Des Moines, Iowa, and Ames, Iowa, earlier in the day.

AJ Rabinowitz of Ocean County, New Jersey, cheers as presidential hopeful Ted Cruz is announced as winner of the Iowa caucus at the Iowa State Fair Elwell Center in Des Moines, Iowa, Monday, Feb. 1, 2016.

AJ Rabinowitz of Ocean County, New Jersey, cheers as presidential hopeful Ted Cruz is announced as winner of the Iowa caucus at the Iowa State Fair Elwell Center in Des Moines, Iowa, Monday, Feb. 1, 2016.

Democratic presidential candidate Hillary Clinton takes photos with supporters and shakes hands after speaking at the 49th annual Salute to Labor Chicken Fry at Illiniwek Park in Hampton, Illinois, Monday, September 5, 2016. The presidential hopeful returned to the event for the second consecutive year after campaigning in both Pennsylvania and Ohio earlier in the day.

Democratic presidential candidate Hillary Clinton takes photos with supporters and shakes hands after speaking at the 49th annual Salute to Labor Chicken Fry at Illiniwek Park in Hampton, Illinois, Monday, September 5, 2016. The presidential hopeful returned to the event for the second consecutive year after campaigning in both Pennsylvania and Ohio earlier in the day.

President Donald Trump speaks to supporters at a campaign rally at the U.S. Cellular Center in Cedar Rapids, Wednesday, June 21, 2017.

President Donald Trump speaks to supporters at a campaign rally at the U.S. Cellular Center in Cedar Rapids, Wednesday, June 21, 2017.

Sen. Bernie Sanders walks up to take the stage outside Modern Woodmen Park in Davenport, Friday, November 4, 2016. The Hillary Clinton campaign held the Davenport Stronger Together Rally with Senator Bernie Sanders to encourage Iowans to vote early and support Clinton.

Sen. Bernie Sanders walks up to take the stage outside Modern Woodmen Park in Davenport, Friday, November 4, 2016. The Hillary Clinton campaign held the Davenport Stronger Together Rally with Senator Bernie Sanders to encourage Iowans to vote early and support Clinton.

Presidential candidate Martin O'Malley shakes hands and meets guests after speaking at Backpocket Brewing in Coralville, Illinois, Saturday Jan. 23, 2016. The former Maryland governor made a stop as a part of "O'Malley Unplugged: The New Leadership Tour" with only nine days left until the Iowa Caucus.

Presidential candidate Martin O'Malley shakes hands and meets guests after speaking at Backpocket Brewing in Coralville, Illinois, Saturday Jan. 23, 2016. The former Maryland governor made a stop as a part of "O'Malley Unplugged: The New Leadership Tour" with only nine days left until the Iowa Caucus.

Attendees gather at barricade for a chance to meet presidential hopeful Donald Trump after his rally at the Veterans Memorial building in Cedar Rapids, Iowa, Saturday, Dec. 19, 2015. Trump held the rally in Cedar Rapids just a few days after a recent GOP Republican debate and used the chance to talk about the debate as well as his hopes and ideas for the United States.

Attendees gather at barricade for a chance to meet presidential hopeful Donald Trump after his rally at the Veterans Memorial building in Cedar Rapids, Iowa, Saturday, Dec. 19, 2015. Trump held the rally in Cedar Rapids just a few days after a recent GOP Republican debate and used the chance to talk about the debate as well as his hopes and ideas for the United States.

Volunteer Mark Rovinski of Springfield, Pennsylvania tosses a bacon treat for his yellow lab, Halley, before an event for presidential candidate Jeb Bush at the campaign's Cedar Rapids, Iowa, field office, Sunday, Jan. 31, 2016. The former Florida Governor made the stop in Cedar Rapids to deliver a brief speech and meet potential caucus goes the day before the Iowa Caucus.

Volunteer Mark Rovinski of Springfield, Pennsylvania tosses a bacon treat for his yellow lab, Halley, before an event for presidential candidate Jeb Bush at the campaign's Cedar Rapids, Iowa, field office, Sunday, Jan. 31, 2016. The former Florida Governor made the stop in Cedar Rapids to deliver a brief speech and meet potential caucus goes the day before the Iowa Caucus.

Sen. Ted Cruz speaks to a crowd packed in the Depot Express gas station in Van Horne, Iowa, Sunday, Nov. 29, 2015. The presidential hopeful made a stop at the Depot Express gas station to give a speech and answer questions with gathered community members and supporters.

Sen. Ted Cruz speaks to a crowd packed in the Depot Express gas station in Van Horne, Iowa, Sunday, Nov. 29, 2015. The presidential hopeful made a stop at the Depot Express gas station to give a speech and answer questions with gathered community members and supporters.

Mary Larew of Iowa City, Iowa, holds a sign in protest of Sen. Marco Rubio outside the Mediacom Outdoor Club in Kinnick Stadium in Iowa City, Iowa, Thursday, Dec. 10, 2015. The republican presidential hopeful made a stop in Iowa City for a meet and greet after visiting Des Moines and Ames earlier in the day.

Mary Larew of Iowa City, Iowa, holds a sign in protest of Sen. Marco Rubio outside the Mediacom Outdoor Club in Kinnick Stadium in Iowa City, Iowa, Thursday, Dec. 10, 2015. The republican presidential hopeful made a stop in Iowa City for a meet and greet after visiting Des Moines and Ames earlier in the day.

Sen. Bernie Sanders is seen speaking from behind a press riser outside Modern Woodmen Park in Davenport, Friday, November 4, 2016. The Hillary Clinton campaign held the Davenport, Iowa, Stronger Together Rally with Senator Bernie Sanders to encourage Iowans to vote early and support Clinton.

Sen. Bernie Sanders is seen speaking from behind a press riser outside Modern Woodmen Park in Davenport, Friday, November 4, 2016. The Hillary Clinton campaign held the Davenport, Iowa, Stronger Together Rally with Senator Bernie Sanders to encourage Iowans to vote early and support Clinton.

Leonard and Mary Ann Verdeck of Cedar Rapids sit waiting for Republican Party Presidential Nominee Donald Trump to arrive at the McGrath Amphitheater in Cedar Rapids, Friday, October 28, 2016.

Leonard and Mary Ann Verdeck of Cedar Rapids sit waiting for Republican Party Presidential Nominee Donald Trump to arrive at the McGrath Amphitheater in Cedar Rapids, Friday, October 28, 2016.

Linn-Mar junior Angel Trachta, 16, takes a selfie behind presidential hopeful Bernie Sanders after a campaign stop at Strawberry Hill Elementary in Anamosa, Iowa, Saturday, Dec. 12, 2015. Vermont Sen. Bernie Sanders made a campaign stop in Anamosa to hold a forum on racial justice and prison reform.

Linn-Mar junior Angel Trachta, 16, takes a selfie behind presidential hopeful Bernie Sanders after a campaign stop at Strawberry Hill Elementary in Anamosa, Iowa, Saturday, Dec. 12, 2015. Vermont Sen. Bernie Sanders made a campaign stop in Anamosa to hold a forum on racial justice and prison reform.

Supporters file in to hear President Donald Trump speak at the U.S. Cellular Center in Cedar Rapids, Iowa, Wednesday, June 21, 2017.

Supporters file in to hear President Donald Trump speak at the U.S. Cellular Center in Cedar Rapids, Iowa, Wednesday, June 21, 2017.

Former U.S. Secretary of State Madeleine Albright's famous pins are accompanied by a Hillary Clinton pin as she speaks at the Hillary for Iowa office in Cedar Rapids, Iowa, Sunday Jan. 17, 2016. Albright spoke to the crowded room about her close ties with the Clintons after serving as the first female U.S. Secretary of State while President Bill Clinton was in office. She used the opportunity to speak about presidential candidate Hillary Clinton's policies and to answer questions on her behalf.

Former U.S. Secretary of State Madeleine Albright's famous pins are accompanied by a Hillary Clinton pin as she speaks at the Hillary for Iowa office in Cedar Rapids, Iowa, Sunday Jan. 17, 2016. Albright spoke to the crowded room about her close ties with the Clintons after serving as the first female U.S. Secretary of State while President Bill Clinton was in office. She used the opportunity to speak about presidential candidate Hillary Clinton's policies and to answer questions on her behalf.

Caroline Cruz, 7, appears on stage with mother, Heidi, and father, presidential hopeful Ted Cruz, as he delivers a victor speech at the Iowa State Fair Elwell Center in Des Moines, Iowa, Monday, Feb. 1, 2016.

Caroline Cruz, 7, appears on stage with mother, Heidi, and father, presidential hopeful Ted Cruz, as he delivers a victor speech at the Iowa State Fair Elwell Center in Des Moines, Iowa, Monday, Feb. 1, 2016.

Donald Trump waves back to the crowd before getting in a car to be driven to his plane after holding a rally at the Synergy Flight Center in Bloomington Sunday, March, 12, 2016.

Donald Trump waves back to the crowd before getting in a car to be driven to his plane after holding a rally at the Synergy Flight Center in Bloomington Sunday, March, 12, 2016.

Donald Trump rally attendees wait in line next to a collection of discarded drinks, umbrellas, signs, and other items not to be allowed into the rally at the Synergy Flight Center in Bloomington, Illinois, Sunday, March, 12, 2016.

Donald Trump rally attendees wait in line next to a collection of discarded drinks, umbrellas, signs, and other items not to be allowed into the rally at the Synergy Flight Center in Bloomington, Illinois, Sunday, March, 12, 2016.

Former President Bill Clinton speaks to a crowd of 450 guests at Northwest Junior High School in Coralville, Iowa, Friday, Jan. 15, 2016. Clinton held an organizing event to campaign on behalf of his wife, Democratic presidential candidate Hillary Clinton, with just 17 days left before the Iowa Caucus.

Former President Bill Clinton speaks to a crowd of 450 guests at Northwest Junior High School in Coralville, Iowa, Friday, Jan. 15, 2016. Clinton held an organizing event to campaign on behalf of his wife, Democratic presidential candidate Hillary Clinton, with just 17 days left before the Iowa Caucus.

Presidential hopeful Bobby Jindal engages with members of the audience at the Shores Event Center in Cedar Rapids, Iowa, October 1, 2015. The Louisiana governor made a stop in Cedar Rapids to speak to a crowd of over 70 people and take questions from the crowd.

Presidential hopeful Bobby Jindal engages with members of the audience at the Shores Event Center in Cedar Rapids, Iowa, October 1, 2015. The Louisiana governor made a stop in Cedar Rapids to speak to a crowd of over 70 people and take questions from the crowd.

Attendees wait in line outside the U.S. Cellular Center in Cedar Rapids to hear President Donald Trump speak at a campaign rally, Wednesday, June 21, 2017.

Attendees wait in line outside the U.S. Cellular Center in Cedar Rapids to hear President Donald Trump speak at a campaign rally, Wednesday, June 21, 2017.