General elections

FILE - In this Oct. 29, 2019, file photo, former President Barack Obama speaks during the Obama Foundation Summit at the Illinois Institute of Technology in Chicago. Obama reiterated a warning about the adoption of “purity tests” in the Democratic presidential primary, which he said are likely to alienate voters needed to defeat President Donald Trump next year. (Ashlee Rezin Garcia/Chicago Sun-Times via AP)

FILE - In this March 23, 2015 file photo, California Supreme Court Chief Justice Tani Cantil-Sakauye delivers her State of the Judiciary address before a joint session of the Legislature at the Capitol in Sacramento, Calif. California's Supreme Court rejected a state law that would have required President Donald Trump to disclose his tax returns to appear as a candidate in the state's primary election next spring. The justices on Thursday said the law that would have required tax returns for all presidential and gubernatorial candidates to appear on the primary ballot was unconstitutional. A federal judge had temporarily blocked the state law in response to a different lawsuit. (AP Photo/Rich Pedroncelli, File)

Former White House national security aide Fiona Hill, left, and David Holmes, a U.S. diplomat in Ukraine, are sworn in to testify before the House Intelligence Committee on Capitol Hill in Washington, Thursday, Nov. 21, 2019, during a public impeachment hearing of President Donald Trump's efforts to tie U.S. aid for Ukraine to investigations of his political opponents. (AP Photo/Andrew Harnik)

Democratic presidential candidates from left, Sen. Cory Booker, D-N.J., Rep. Tulsi Gabbard, D-Hawaii, Sen. Amy Klobuchar, D-Minn., South Bend, Ind., Mayor Pete Buttigieg, Sen. Elizabeth Warren, D-Mass., former Vice President Joe Biden, Sen. Bernie Sanders, I-Vt., Sen. Kamala Harris, D-Calif., former technology executive Andrew Yang and investor Tom Steyer wave to the audience before a Democratic presidential primary debate, Wednesday, Nov. 20, 2019, in Atlanta. (AP Photo/John Amis)

Democratic presidential candidate Sen. Amy Klobuchar, D-Minn., center speaks as Democratic presidential candidate Rep. Tulsi Gabbard, D-Hawaii, left and Democratic presidential candidate South Bend, Ind., Mayor Pete Buttigieg listen during a Democratic presidential primary debate, Wednesday, Nov. 20, 2019, in Atlanta. (AP Photo/John Bazemore)

U.S. Secretary of State Mike Pompeo talks to journalists during a news conference during a NATO Foreign Ministers meeting at the NATO headquarters in Brussels, Wednesday, Nov. 20, 2019. (AP Photo/Francisco Seco)

Ambassador Kurt Volker, left, former special envoy to Ukraine, and Tim Morrison, a former official at the National Security Council are sworn in to testify before the House Intelligence Committee on Capitol Hill in Washington, Tuesday, Nov. 19, 2019, during a public impeachment hearing of President Donald Trump's efforts to tie U.S. aid for Ukraine to investigations of his political opponents.(AP Photo/Susan Walsh)

Former Massachusetts Gov. Deval Patrick, left, speaks with a business owner during a campaign stop, Tuesday, Nov. 19, 2019, in Columbia, S.C. (AP Photo/Meg Kinnard)

Democratic presidential candidates chosen to participate in fifth debate;

Democratic presidential candidate former Massachusetts Gov. Deval Patrick speaks to local residents during a stop at the Sykora Bakery, Monday, Nov. 18, 2019, in Cedar Rapids, Iowa. (AP Photo/Charlie Neibergall)