2012 United States presidential election

Sen. Elizabeth Warren, D-Mass., acknowledges cheers as she takes the stage during an event to formally launch her presidential campaign, Saturday, Feb. 9, 2019, in Lawrence, Mass. (AP Photo/Elise Amendola)

Former San Antonio Mayor and Housing and Urban Development Secretary Julian Castro, center right, is embraced by his twin brother U.S. Rep. Joaquin Castro (D-San Antonio), center left, during an event where Julian Castro announced his decision to seek the 2020 Democratic presidential nomination, Saturday, Jan. 12, 2019, in San Antonio. (AP Photo/Eric Gay)

FILE - In this Dec. 8, 2016 file photo then Sen. Harry Reid, D-Nev., speaks during a ceremony on Capitol Hill in Washington. Reid said Thursday, Jan. 10, 2019, he thinks President Donald Trump has no conscience and he'd like to see Utah Sen. Mitt Romney run against Trump in 2020 for the GOP nomination for president. The 79-year-old Democrat, who served as Senate Majority Leader, said in a radio interview with KNPR in Nevada that the partial government shutdown over Trump's push for a U.S.-Mexico border wall is an example of Trump's behavior.(AP Photo/Evan Vucci, File)

File-This Oct. 9, 2018, file photo shows Republican U.S. Senate candidate Mitt Romney answering a question about tariffs during the debate with Democratic opponent Jenny Wilson in the America First Event Center in Cedar City, Utah. Utah Sen.-elect Romney says President Donald Trump's "conduct over the past two years ... is evidence that the president has not risen to the mantle of the office." Romney, who was the Republican presidential nominee in 2012, is praising some of Trump's policy decisions in a Washington Post op-ed published Tuesday, Jan. 1, 2019. But he adds: "With the nation so divided, resentful and angry, presidential leadership in qualities of character is indispensable. And it is in this province where the incumbent's shortfall has been most glaring."(James M. Dobson/The Spectrum via AP, File)

File-This Oct. 9, 2018, file photo shows Republican U.S. Senate candidate Mitt Romney answering a question about tariffs during the debate with Democratic opponent Jenny Wilson in the America First Event Center in Cedar City, Utah. Utah Sen.-elect Romney says President Donald Trump's "conduct over the past two years ... is evidence that the president has not risen to the mantle of the office." Romney, who was the Republican presidential nominee in 2012, is praising some of Trump's policy decisions in a Washington Post op-ed published Tuesday, Jan. 1, 2019. But he adds: "With the nation so divided, resentful and angry, presidential leadership in qualities of character is indispensable. And it is in this province where the incumbent's shortfall has been most glaring."(James M. Dobson/The Spectrum via AP, File)

In this Dec. 18, 2018, photo, President Donald Trump speaks during a roundtable discussion on the Federal Commission on School Safety report, in the Roosevelt Room of the White House in Washington. Republicans in early-voting states are grappling with how _ and whether _ to protect Trump from a potential primary challenger in 2020. South Carolina GOP leaders said Wednesday they were considering cancelling their presidential primary. (AP Photo/Evan Vucci)

Democrat Julian Castro poses for a photo at his home in San Antonio, Tuesday, Dec. 11, 2018. Castro says he is launching a presidential exploratory committee ahead of a likely White House run in 2020. Castro was the nation’s housing secretary until 2016 and spent five years as mayor of San Antonio. (AP Photo/Eric Gay)

Speaker of the House Paul Ryan, of Wis., speaks after Secretary of Defense Jim Mattis awarded him with the Department of Defense Medal for Distinguished Public Service at the Pentagon, in Washington, Wednesday, Nov. 28, 2018. (AP Photo/Cliff Owen)