House Speaker Nancy Pelosi's decision to send articles of impeachment to the Senate ends her long standoff with Senate Republican Majority Leader Mitch McConnell, clearing the way for a Senate trial. But it couldn't come at a worse time for Minnesota U.S. Sen. Amy Klobuchar, one of four senators contending for the Democratic presidential nomination.

The trial of President Donald Trump, which Senate Republicans might be eager to put behind them, could come in the next few weeks. That's just as the Democratic candidates are making their final pitches to voters in Iowa, where the first-in-the-nation caucuses take place on Feb. 3.

Sidelined from the campaign trail for an undetermined amount of time would be Klobuchar plus Sens. Bernie Sanders, Elizabeth Warren and Cory Booker, who is lagging in the polls but still looks and acts like he's in the race.

The timing is doubly bad for Klobuchar, who has been experiencing a wave of momentum since strong debate performances in November and December.

Despite some recent gains in the polls and the money chase, Klobuchar still has a lot of ground to make up to stay competitive with the race's top tier of Warren, Sanders, former Vice President Joe Biden and former South Bend, Ind., Mayor Pete Buttigieg.

And Iowa clearly is her most favorable ground.