A week from tonight, Iowa Democrats plan to gather in high school gymnasiums, public libraries, church basements and other locales to make the first concrete decisions of the 2020 presidential election. And in the final days before the caucuses, former Vice President Joe Biden enjoys a distinct advantage, having much of the state to himself while the senators running for president are stuck in Washington with the impeachment trial. Even though he's not at the trial, we can expect Biden to keep at least some of his focus on the proceedings — even as he said today he doesn't see a need to appear.

"I have nothing to defend," Biden told CBS News campaign reporter Bo Erickson. "This is all a game." Erickson followed up, asking Biden whether he'd want to appear if his name comes up during the trial. "Even if they bring me up! Nobody has said I have done anything wrong, period. What is there to defend? This is all — the only reason he is being impeached is that he tried to get another government to smear me and they wouldn't."

Sure enough, Trump impeachment lawyer Pam Bondi did bring up the Biden family on Monday in relation to Hunter Biden's work in Ukraine. The Biden campaign quickly responded, saying Bondi's allegations amounted to a "conspiracy theory" that had already been debunked.

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The Iowa Caucus very much remains a jump-ball, with the former vice president narrowly trailing or tied with Senatot Bernie Sanders and former South Bend Mayor Pete Buttigieg still in the hunt. Senators Elizabeth Warren and Amy Klobuchar are also factors - especially if one or both of them fail to garner the 15 percent required to accrue delegates, forcing their supporters to pick a second choice.

Biden's comments this morning come as multiple senior campaign aides tell CBS News political correspondent Ed O'Keefe that their goal for the closing week is to keep their entire operation focused on a "Biden can beat Trump" message across the airwaves, on the stump and as volunteers and staffers make calls or send texts to voters. That a separate pro-Biden PAC is running television ads with a similar message across Iowa doesn't hurt, either.

At the same time, any deviation from this plan — if Biden makes a verbal or factual stumble, or an opponent levels a new attack, or if there's an unhelpful a wrinkle for them in the impeachment trial — could imperil the campaign's home-stretch appeal to Iowans.

FROM THE CANDIDATES

AMY KLOBUCHAR

Minnesota Senator Amy Klobuchar believes Iowa voters should choose her over former Vice President Joe Biden not only because she represents a new generation, but also because she has learned to work with a Republican Party reshaped by President Trump.

"Of course he has vast experience, and our country has benefited because of that," Klobuchar said of Biden Sunday evening in an interview with CBS News political correspondent Ed O'Keefe. "But I have had the experience of governing in the last few years with Donald Trump, and I've seen what's motivating my Republican colleagues firsthand — the bad of it — but I've also figured out ways you can get through." Klobuchar noted the president has signed more than 30 bills into law where she was the lead Democratic sponsor.

CBS News producer Rebecca Kaplan says the latest CBS News battleground tracker has Klobuchar with 7% support among likely Democratic voters in Iowa. She trails Biden, with 25% support, and South Bend, Indiana Mayor Pete Buttigieg, with 22% support, in the hunt for Iowa's more moderate Democrats. Like all of the lower-performing candidates in the race, she stands to benefit from the fact that just 35% of likely voters say they've definitely made up their mind about who they will support. But if she remains stuck in single digits, Klobuchar is in trouble: Candidates can only walk away from Iowa with all-important delegates if they win at least 15% support.

Her criticism isn't just reserved for her fellow moderates. Klobuchar also said she had "a big issue" with the fact that her fellow senator, Vermont's Bernie Sanders, told "CBS Evening News" anchor Norah O'Donnell last Friday that it was "impossible to predict" how much his Medicare-for-All plan would cost. "Do you know exactly what health care costs will be, one minute, in the next 10 years if we do nothing? It will be a lot more expensive than a Medicare-for-all single-payer system," Sanders said.

Klobuchar said that sounds far too much like President Trump's promises. "That is the difference between a plan and a pipe dream," she said. "We already have someone that's running up the debt in the White House and Donald Trump has been treating people like poker chips in one of his bankrupt casinos. I think it is really important that we have a candidate leading the ticket who is going to be able to take on Donald Trump on that very issue."

She added, "He says all this stuff. And then he refused to pay for it, or he adds it to the debt or burdens the shoulders of kids. I don't think that's the way to do it, and I think you have to be really straightforward. You just can't say I'll figure that out later. You have to show how you're going to pay for things, and I've done that."

Sanders, Klobuchar and two other senators, Elizabeth Warren of Massachusetts and Michael Bennett of Colorado, have all been pulled away from the campaign trail in the final two weeks of the Iowa caucus by president's impeachment trial, which demands their participation six days a week. And while Klobuchar has been holding tele-town halls and dispatching surrogates across the state, she's the one who likely suffers the most from the time way from the state.

So, in the limited time she had during the trial, she spent her 36 hours campaigning in Iowa this weekend to appeal to her supporters for help on the ground. "I've always believed the obstacles on the path aren't obstacles. They are the path. I am good at those events. I like talking to people. I like making my case," she said.

"We are getting bigger and bigger crowds and still having people come and say, 'I hadn't heard you before. I've heard 10 candidates, and I'm going to support you.' That happened in Waterloo. And so, I know what I'm missing out on, because for me this is a unique part of my campaigning that kind of was crescendoing to the end. But it is my job. I've got to go do my job, and I'm one of 100 jurors…I'm certainly not going to shirk my duties at this constitutional crisis moment for country."

ELIZABETH WARREN

Elizabeth Warren will be in Washington for the impeachment trial even if it keeps her out of Iowa on caucus day "so long as we've got a real trial going on," she told CBS News campaign reporter Zak Hudak on the way into the trial Monday. "I have a responsibility to be here," she said, referring to the trial.

Warren had not previously set any caveats to her presence at the trial, but on Sunday, her campaign added new events – "subject to change depending on impeachment" – in Western Iowa in Thursday. Asked again by another reporter whether that would be the case even on caucus day, Warren said, "I have a responsibility. If we have a real trial going on, that's my job."

Warren also said that former National Security Adviser John Bolton's reported admission in his book that Trump had told him in August to withhold aid to Ukraine unless the country agreed to investigate his Democratic rivals had worked Republicans into a corner. "I think that really puts it to the Republicans," she said. "You said no direct evidence. And now we've got somebody saying that they have the direct evidence."

Asked about Bolton's credibility, Warren said cross examination is necessary to establish credibility or lack thereof. "Wasn't that one of the things that the Republican attorney said on Saturday?" she asked. "That cross examination was the crucible of truth. Well, let's get the witness in, let's swear him in. Let's do a little cross examination."

Separately CBS News campaign reporter Alex Tin says Elizabeth Warren is up on television with her first Spanish language ad in Nevada: "Elizabeth Warren es una luchadora." While Warren is far from the first candidate to court Spanish-speakers on Nevada's airwaves, Kantar Media data shows Warren's latest $161,560 buy does not include time on the state's popular Spanish-language television or radio stations. For example: only Tom Steyer, who tore through a packed schedule of campaign events over the weekend in Nevada, has bought ads on the Univision station in Las Vegas this week.

STATE-BY-STATE

CALIFORNIA

Officials in a Bay Area county tell CBS News campaign reporter Alex Tin that Super Tuesday has already started in California, with mail ballots arriving in Solano County mailboxes as early as Friday last week. While voting in the massive primary officially starts on February 3rd, counties are permitted by state law to begin delivering ballots as early as they are ready, making California the latest state to already kick off early voting. And a handful of candidates are already courting votes in California, Michael Bloomberg on Monday rolling out his latest congressional endorsement in the state.

IOWA

With a week to go until the Iowa caucuses, CBS News campaign reporter Adam Brewster says candidates are beginning to roll out their closing arguments on the airwaves as they try to pick off undecided caucus-goers. Former South Bend Mayor Pete Buttigieg's ad, "It's Time," makes the case that Washington needs a new generation of leadership.

"It's time to turn the page from a Washington experience paralyzed by the same old thinking, polarized by the same old fights, to a bold vision for the next generation," Buttigieg says in the ad, which will run across the state through Caucus Night. Senator Elizabeth Warren's campaign rolled out two new ads in Iowa. One, called "Betsy," features testimonials from some of Warren's family members, including her Republican brothers, about why they'd vote for her.

The other ad, "Why She Will Beat Him," compares Warren's upbringing and record to President Trump's. And the conservative political action group Club For Growth is up on the air in Iowa, with an ad going after Senator Bernie Sanders' plans for healthcare and fighting climate change. According to Kantar/CMAG, the group has purchased about $41,000 worth of airtime in Iowa in the week leading up to the caucuses.

CONGRESSIONAL COVERAGE

IN THE SENATE

Following the report that former National Security Advisor John Bolton says in an upcoming book that the president conditioned aid to Ukraine on an investigation into the Biden family, Republican Senator Susan Collins said, "The reports about John Bolton's book strengthen the case for witnesses and have prompted a number of conversations among my colleagues." Collins, who is facing a reelection battle in Maine later this year, has been one of the Republicans who has signaled she is open to witness testimony.

If all Democrats vote to hear from witnesses following the opening arguments, they only need four Republican votes to force the body to call witnesses. Collins, along with Senators Mitt Romney, Lisa Murkowski, and Lamar Alexander. are the senators who have previously said they would consider hearing from more witnesses.

Senator Kelly Loeffler, the chamber's newest member, broke from Senate norms in calling out Senator Mitt Romney, her fellow Republican, for indicating he would like to hear from more witnesses, reports CBS News political unit associate producer Eleanor Watson. Attacking a member of the same party is unusual, but more than that, Loeffler is going after someone she once supported with over half a million dollars. Loeffler donated over $750,000 to Restore Our Future, the super PAC affiliated with Mitt Romney's 2012 presidential campaign.

Loeffler was not President Trump's first choice to replace U.S. Senator Johnny Isakson following his retirement at the end of last year, but he has recently taken notice of her Twitter activity, even retweeting her over the weekend. Loeffler was appointed by Governor Kemp to fill Isakson's seat and will have to win reelection on her own later this year. Republicans allied with Mr. Trump have criticized Loeffler for not whole-heartedly backing the president and have urged Representative Doug Collins to challenge her in a primary.

IN THE HOUSE

Continuing their focus on healthcare from the 2018 midterms, the Democratic Congressional Campaign Committee announced a seven-figure ad buy, their most expensive one yet, calling out Republicans for not taking action on H.R.3, the House-passed legislation to lower drug costs.

The bilingual ads, running on cable networks and in 14 markets, tie Mitch McConnell and Senate Republicans to money from drug companies. "It's time for Mitch McConnell and the Republicans to start working for us. Not the special interests," the 30-second ad says.

In a call with reporters on Monday, CBS News political unit broadcast associate Aaron Navarro says DCCC Chair Cheri Bustos said the ads are not a response to the impeachment ads Republican groups have been running in Trump-won Democratic districts. "They got a losing message on impeachment, we know it's not working," she said. "Washington Republicans and Donald Trump are freaking out, because they are on the wrong side of this prescription drug argument."

Bustos and DCCC executive director Lucinda Guinn made clear that healthcare will be the number one issue they will run on in 2020, and pointed to polling that shows Democrats have a 16-point advantage when it comes to trust on the issue of drug prices. Right after H.R.3's passage in December 2019, the DCCC launched a modest five-figure digital ad campaign in competitive "Frontline" districts with incumbents. Last week, they targeted 11 House Republican districts and ran digital ads highlighting Trump's comments that he would consider cuts to Medicare.