Six Democratic challengers to Republican President Donald Trump are squaring off in a high-stakes debate late Tuesday, their last face-to-face encounter before voters in the Midwestern farm state of Iowa start to pick a Democratic nominee to oppose Trump in the November national election.Iowa, with its mostly rural landscape and a predominantly white population of about 3 million, is hardly reflective of the United States as a whole. But once every four years it has an out-sized importance in the U.S. presidential race as the first state to vote in the months-long nominating process for both Republicans and Democrats. This time caucus voting takes place on the night of Feb. 3.Trump is a shoo in for renomination to a second four-year term in the White House. But the Democratic race is highly unsettled.FILE PHOTO: Democratic U.S. presidential candidate and former U.S. Vice President Joe Biden speaks during a town hall in Independence, Iowa, U.S. Jan. 3, 2020.Former Vice President Joe Biden, now in his third race for the party’s presidential nomination, leads national polls of Democratic voters, but possibly trails his Democratic opponents in Iowa and some other states.Should he falter early in the nominating process, that could dent his key campaign argument that according to national polls he stands the best chance of defeating Trump.Last weekend’s Iowa Poll shows Sen. Bernie Sanders of Vermont, a self-described democratic socialist, surging to a narrow lead, with 20% support in the state. Progressive Sen. Elizabeth Warren of Massachusetts is second at 17%, ahead of former South Bend, Ind., Mayor Pete Buttigieg, who has fashioned himself as a political centrist, at 16% and Biden, a left-of-center politician through nearly five decades in Washington, at 15%.Democratic presidential candidate Sen. Bernie Sanders, I-Vt., smiles as he listens to a question from the audience during a campaign stop, Nov. 24, 2019, in Hillsboro, N.H.“There’s no denying that this is a good poll for Bernie Sanders,”  pollster Ann Selzer, told the Des Moines Register, which is sponsoring the debate along with television network CNN. “He leads, but it’s not an uncontested lead. He’s got a firmer grip on his supporters than the rest of his compatriots.”But more than half of those polled said they could still decide to support a candidate other than the one they now prefer or have yet to make up their mind, a fluid state of political sentiment that likely increases the importance of Tuesday’s six-way debate.A Monmouth University poll on Monday showed different results, with Biden ahead, in order, over Sanders, Buttigieg and Warren.Sen. Amy Klobuchar of Minnesota and wealthy entrepreneur Tom Steyer, both trail the four leaders in the pre-election Iowa polling, but qualified for the debate stage by meeting the polling and fundraising standards set by the national Democratic Party. Other Democratic candidates remain in a crowded field of presidential aspirants, but did not make the cut for the debate or have dropped out, including Sen. Cory Booker of New Jersey who left the race on MondaySanders and Warren are longtime friends who hold similar liberal viewpoints, such as their call, with some variations, for adoption of a government-run national health care system and an end to the country’s private insurance company system to pay health care bills. As such, they have mostly adhered to a non-aggression pact with each other in earlier debates leading up to Tuesday’s showdown ahead of the Iowa vote.FILE PHOTO: Democratic 2020 U.S. presidential candidate and U.S. Senator Elizabeth Warren delivers a speech, on the one year anniversary of announcing her campaign, at Old South Meeting House in Boston, Dec. 31, 2019.But over the weekend, Warren accused Sanders of sending his supporters in Iowa out to meet voters with specific talking points “to trash me.” The talking points claimed that Warren could not attract more Democratic voters in a race against Trump because she is elitist, “supported only by highly educated, more affluent people who are going to show up and vote Democratic no matter what.”Sanders brushed off the criticism, saying, “We have over 500 people on our campaign. People do certain things. I’m sure that on Elizabeth’s campaign people do certain things as well.””But you’ve heard me for months,” Sanders added, “I have never said a negative word about Elizabeth Warren, who is a friend of mine. We have differences on issues. That’s what a campaign is about.”Meanwhile, news reports Monday claim that in a private meeting in 2018,  Sanders reportedy told Warren that he did not think a woman could win the presidency.Warren subsequently told associates about Sanders’s comment, The New York Times reported,  citing people with knowledge of her remarks.In a statement, Sanders denied the report saying it was “ludicrous” to think he would have made such a comment. “Do I believe a woman can win in 2020? Of course! After all, Hillary Clinton beat Donald Trump by three million votes in 2016.”Trump has also taken note of Sanders’s recent ascent in opinion polls, saying in a Twitter comment over the weekend, “Wow! Crazy Bernie Sanders is surging in the polls, looking very good against his opponents in the Do Nothing Party. So what does this all mean? Stay tuned!” Wow! Crazy Bernie Sanders is surging in the polls, looking very good against his opponents in the Do Nothing Party. So what does this all mean? Stay tuned!— Donald J. Trump (@realDonaldTrump) Senator Amy Klobuchar speaks during the U.S. Democratic presidential candidates debate at the Tyler Perry Studios in Atlanta, Nov. 20, 2019.Three of the leading Democratic challengers – Sanders, Warren and Klobuchar – could be directly affected by Trump’s impeachment trial since they will be among the 100 members of the Senate deciding Trump’s fate, keeping them in Washington six days a week while the trial is going on, and importantly for them, off the campaign trail in Iowa to meet voters.With a Republican majority in the Senate, Trump is all assured of being acquitted and allowed to remain in office to face voters in November. But a full-blown trial, if witnesses are called to testify as Democrats and some Republicans want, could infuse unexpected new information about Trump and perhaps Biden into the last weeks of the Iowa contest.In some states there are party primary elections, but in Iowa, Democrats will have caucuses throughout the state, with the candidates pushing their supporters to rally at firehouses, schools, churches and other voting places on the night of Feb. 3. Many of the state’s voters are likely to closely watch Tuesday as the candidates tangle over health care policies, national security, Trump’s drone strike killing a top Iranian general and an array of other issues.Other state nominating contests follow quickly after and the importance of the Iowa vote will soon be eclipsed. But until then, its quadrennial centrality to the American presidential political scene cannot be denied.  
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