The Note: Pelosi's 'forever' impeachment puts GOP on warning There will be a time that President Trump is no longer under active impeachment.

The TAKE with Rick Klein

There will be a time that President Donald Trump is no longer under active impeachment -- a time that is closer than ever, with a Senate trial all but certain to start by the end of this week.

But House Speaker Nancy Pelosi wants it known that being done with impeachment doesn’t take away the stain.

"He will be impeached forever," Pelosi told ABC News Chief Anchor George Stephanopoulos on "This Week" Sunday.

Pelosi is also holding open the possibility of additional subpoenas in the House, which could even lead to more articles of impeachment. And in the more immediate term, the nation’s top elected Democrat is serving notice that the Senate process will matter.

Delaying the articles of impeachment sets up a situation where individual witnesses could be called by the vote of a simple majority. That puts pressure on Senate Majority Leader Mitch McConnell to keep defections below four as names get teed up by Democrats.

"He will be accountable to the American people," Pelosi said of McConnell.

Democrats are still hoping that calling witnesses will change Senate dynamics by establishing new facts. They still know that Trump will almost certainly be acquitted, and that he will declare himself exonerated.

But by putting the trial itself on trial, and keeping open the possibility of more investigating in the House, Democrats are seeking to complicate the path to vindication.

The RUNDOWN with MaryAlice Parks

Sen. Bernie Sanders claims Trump is talking and tweeting about him, because he is nervous, "because they know what we know, and that is that we are the strongest campaign to defeat Donald Trump," the senator said this week.

Sanders' strong showing in the latest Des Moines Register poll over the weekend was a key piece of evidence of his deep support and strong organization in the first caucus state. His team claims their community-organizing tactics are unmatched by others and have brought new voters in the state into the fold.

On the ground in Iowa though, it is clear other campaigns are well positioned, too. Three weeks out from the first votes, the race still feels like a total jump ball.

And the pressure is bubbling over.

Sen. Elizabeth Warren blasted Sanders after Politico reported about an alleged script Sanders' team had for volunteers with talking points about her appealing to more affluent voters.

"I was disappointed to hear that Bernie is sending his volunteers out to trash me," Warren said Sunday.

Visibly upset talking to reporters, it now seems the dynamic between them has changed. For months, the two progressive senators have played nice with each other, even gone out of their way to defend each other.

That could -- and very likely will -- be very different at the debate this week.

The TIP with Armando Garcia and Zohreen Shah

At a canvass launch in New Hampshire on Sunday a supporter asked Andrew Yang to campaign there before the Iowa caucus, but said she understood he needed to focus on the Hawkeye State, which votes in three weeks.

"Screw Iowa," Yang joked, but underneath that quip is a very serious concern: He will not be on the Iowa debate stage with other candidates Tuesday. It's the first major blow to a campaign that has unexpectedly drawn overflow crowds in many places and outlasted attempts by sitting senators and governors. Still, he promised to overperform in the first caucus state, saying, "We’re gonna shock the world starting on Feb. 3."

Yang plans to be back in Iowa with campaign stops throughout the state this week. And there could even be a surprise to counterprogram the debate.

"We’re going to do something at least somewhat fun ... you'll find out very soon," he told ABC News.

ONE MORE THING

Texas Democrats, fueled by the party’s nearly quarter-century-held dream of turning Texas blue, are mounting an aggressive ground-game operation with the largest voter registration program in the state's history, according to the state party, as well as an expansive voter protection effort ahead of the 2020 election. Among the groups involved is Fair Fight 2020, the multi-million dollar initiative launched by Stacey Abrams, the former Georgia gubernatorial candidate, which has singled out Texas as one of 20 battleground states.

THE PLAYLIST

ABC News' "Start Here" Podcast. Monday morning’s episode features ABC News’ David Wright and Anne Flaherty. They tell us why House Speaker Nancy Pelosi finally decided to send the articles of impeachment to the Senate, and what comes next. Then, ABC News Deputy Political Director MaryAlice Parks tells us about Sen. Bernie Sanders’ weekend in Iowa amid a surge in the state. http://apple.co/2HPocUL

WHAT YOU NEED TO KNOW TODAY

President Donald Trump will meet with Vice President Mike Pence at the White House at 12:15 p.m. He will depart for Louisiana at 4:15 p.m. to attend college football's National Championship Game between Clemson and LSU at 8 p.m.

Rep. Tulsi Gabbard, D-Hawaii, participates in a politics and government class discussion at River Bluff High School in Lexington, South Carolina, at 9 a.m.

Former Vice President Joe Biden attends a community event with former Secretary of State John Kerry in Knoxville, Iowa, at noon. He then attends a community event with former Secretary of State John Kerry in Marshalltown, Iowa, at 3 p.m.

Former South Bend, Indiana, Mayor Pete Buttigieg leads a town hall in Winterset, Iowa, at 12:30 p.m. He then hosts a town hall in Ames, Iowa, at 6:30 p.m.

Former Rep. John Delaney, D-Md., knocks on doors in Griswold, Iowa, beginning at 2 p.m. Later, he visits the Middle of Nowhere restaurant in Cumberland, Iowa, at 5 p.m.

Andrew Yang leads a town hall in Newton, Iowa, at 4 p.m. He then hosts a town hall in Des Moines, Iowa, at 6 p.m.

Tom Steyer attends a party at climate activist Channing Dutton’s home in Des Moines, Iowa, at 5 p.m.

Former Massachusetts Gov. Deval Patrick attends a "Moms Demand Action Meeting" in Stratham, New Hampshire, at 6 p.m.

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The Note is a daily ABC News feature that highlights the key political moments of the day ahead. Please check back tomorrow for the latest.