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WASHINGTON — Two developments help explain Bernie Sanders’ slight front-runner status in Iowa and New Hampshire.

Development No. 1: Elizabeth Warren’s overall decline, which has enabled to Sanders to solidify his dominance of the Democrats’ progressive lane. (It shouldn’t be a surprise that Sanders’ numbers have increased while Warren’s have gone down.)

Development No. 2: Pete Buttigieg has been holding steady in the first two states, which means that the pragmatic/moderate lane is being split among two viable candidates — with Amy Klobuchar also hitting or nearing double digits.

Indeed, you could argue that Sanders’ best asset right now is Buttigieg. Just take a look inside our NBC News/Marist poll of New Hampshire, which shows Sanders leading in the Granite State:

Sanders outperforms his rivals among self-described progressive voters, who make up 54 percent of the Democratic electorate.

He gets support from 36 percent of these progressives, versus 20 percent for Warren and 12 percent for Buttigieg.

Among more moderate Democratic primary voters (42 percent of the electorate), Biden gets 26 percent to Buttigieg’s 24 percent.

By age, Sanders laps the field with voters under 45 (getting 39 percent support), while Biden and Buttigieg are essentially tied among those 45 and older (19 percent and 18 percent, respectively).

So with seven days to go until Iowa, maybe the biggest question is this one: Does Pete Buttigieg’s support hold — or grow?

Or does the moderate/pragmatic/older lane solidify around one candidate — most likely Biden?

The answer will probably determine the outcome of Iowa and New Hampshire.

Data Download: The number of the day is … 76 percent

76 percent.

That’s the share of Bernie Sanders backers in New Hampshire who say they support him “strongly,” according to the latest NBC News/Marist poll of likely Democratic primary voters in the Granite State.

That’s compared with 56 percent of Biden backers who say the same of their candidate, 53 percent of Warren supporters and just 44 percent of Buttigieg’s backers.

Can I get a witness?

Turning to the impeachment trial, it’s absolutely devastating for President Trump’s lawyers to have argued on Saturday that no single witness has been able to testify that Trump himself tied Ukraine’s security aid to an investigation into the Bidens — and then have this bombshell drop the very next day.

“President Trump told his national security adviser in August that he wanted to continue freezing $391 million in security assistance to Ukraine until officials there helped with investigations into Democrats including the Bidens, according to an unpublished manuscript by the former adviser, John R. Bolton,” the New York Times writes.

What’s even more potentially damning, Bolton said he sent his manuscript to the White House a month ago so it could be reviewed for classified information, which means Trump and his lawyers most likely knew about Bolton’s account — as they’ve been arguing for no new witnesses in the impeachment trial.

Last night, Trump denied telling Bolton Ukraine aid was tied to any Biden investigation. (Then again, Trump also said he didn’t know Lev Parnas, but now we know Trump had dinner with him.)

On “Meet the Press” yesterday, Rep. Adam Schiff, D-Calif., argued that if Democrats are unable to get witnesses like Bolton to testify, Trump will never be exonerated — at least not politically.

“If [Republicans are] successful in depriving the country of a fair trial, there is no exoneration. There is no exoneration,” he said.

But also on “Meet” yesterday, Sen. Mike Braun, R-Ind., explained why it’s going to be so hard for GOP senators to vote for witnesses like Bolton: Their pro-Trump voters won’t allow it.

“For many of us, depending on where you're from -— and this also is not only your own conscience you have to measure here. It is what your constituents [want].”

Braun also said, “So I think when it comes to witnesses, each senator will have to ask with the political exigencies within their own area and the fairness factor.”

Tweet of the day

Note the date, folks. The White House has had this for WEEKS before the Senate trial. Consider everything the Trump legal team said last week with that in mind.... https://t.co/AH5usbkOnJ — Susan Glasser (@sbg1) January 27, 2020

Day 2 for the defense: President Trump’s lawyers will continue their arguments beginning at 1:00 p.m. ET, per NBC’s Kasie Hunt and the NBC Capitol Hill team.

Where are we?

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Last Tuesday: procedural jousting over the organizing resolution; rules passed around 2:00 a.m. ET

Last Wednesday: prosecution opening arguments, 8 hours

Last Thursday: prosecution, 8 hours

Last Friday: prosecution, 8 hours

Last Saturday: White House defense

Sunday: off

Today: White House defense

Tomorrow: White House defense

Wednesday: Senators’ questions

Thursday: Senators’ questions

Friday: Deliberations?

Saturday: Vote on witnesses?

Sunday: off

Monday: Iowa caucuses

Tuesday: State of the Union

2020 Vision: Look at who’s in in Iowa — and who has to remain in DC

On the campaign trail today: With one week to go before the Iowa caucuses, the main activity is in the Hawkeye State – for the non-senators at least: Joe Biden stumps in Cedar Falls, Marion and Iowa City… Pete Buttigieg is in Boone, Iowa Falls, Vinton and North Liberty… And Andrew Yang hits Orange City, Le Mars and Council Bluffs, while Tom Steyer travels to Ames… Outside of Iowa, Michael Bloomberg campaigns in Vermont and Maine… And Tulsi Gabbard stumps in New Hampshire.

Dispatches from NBC’s campaign embeds: Elizabeth Warren changed up her campaign’s message in the final stretch of Iowa, NBC’s Deepa Shivaram reports, now focusing on “Women Win.” Shivaram asked Warren what her strategy will be if her message doesn’t get her ahead of Bernie Sanders in the Iowa caucuses:

Shivaram: "Senator if you don't win Iowa, is that a reason to change your strategy going forward to Super Tuesday?"

Warren: "Look, we have not yet had the caucuses. I am here to be with people, to talk about why I'm in this race. We got a country that works great for billionaires. A country that works great for giant corporations. A country that works great for lobbyists. I think it's time to make this country work great for everybody else. That's why I'm in this fight."

Shivaram: "No reason to change your strategy?"

Warren: "You know, as I said, I'm running a campaign based on a lifetime of fighting for working families. I'm running a campaign from the heart. That's what it's all about for me."

Shivaram: "Do you have a backup plan if you don't place well in Iowa?"

Warren: "This is who I am."

The Lid: Strange bedfellows or a natural alliance?

Don’t miss the pod from Friday, when we looked at the reporting that Kamala Harris might endorse Joe Biden.

ICYMI: News clips you shouldn’t miss

Pete Buttigieg is going on the attack by talking about the “risk” of nominating Bernie Sanders.

Amy Klobuchar says she “should be leading the ticket.”

Biden backers want to be talking about their candidate’s electability, not about his Social Security spat with Bernie Sanders.

If you missed our New Hampshire poll over the weekend, check it out here.

And don’t miss the Des Moines Register’s endorsement of Elizabeth Warren from Saturday night.

Back in 2016, Trump attorney Alan Dershowitz called Trump “destabilizing and unpredictable.”

Trump Agenda: Pompeo vs. NPR

Don’t miss the latest in the Mike Pompeo vs. NPR controversy.

The president implied over the weekend that Adam Schiff should pay a “price” for his role in the impeachment inquiry.

Rep. Jerry Nadler will miss today’s impeachment trial due to his wife’s cancer treatment.

2020: Weekend at Bernie’s

The Democratic Party establishment is still flummoxed by how to deal with Bernie Sanders, writes POLITICO.

Pete Buttigieg made his case on Fox News over the weekend.

Alex Seitz-Wald asks if Bloomberg’s millions really are a threat to Trump.

Bloomberg talked over the weekend about anti-Semitic violence.

A fifth member of Congress has endorsed Bloomberg.