“I’m in Texas and they have a saying here: ‘Don’t Mess with Texas.’ Well, I say, ‘Don’t Mess with the Constitution, Mr. President,’ Pelosi told fellow Democrats, according to an aide on the call.

Illinois Rep. Cheri Bustos, who leads House Democrats’ campaign arm, advised the caucus’ most vulnerable members to gauge support and test their message through polling in their respective districts — surveys that the Democratic Congressional Campaign Committee would help fund, according to multiple people on the call. She also said the campaign arm could deploy digital ads in the future.

Bustos also shared the results of the DCCC’s first poll focused on impeachment since Pelosi formalized an inquiry last week. The poll found that 54 percent of likely voters support Democrats’ inquiry, according to a summary obtained by POLITICO.

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Top Democrats used Sunday’s conference call to formalize their caucus’ messaging operation on impeachment with more focused talking points. It came after leaders faced blowback from some lawmakers, particularly those from swing districts, over past messaging stumbles.

Democratic Caucus Chairman Hakeem Jeffries outlined a plan to message the issue with “repetition,” according to multiple people on the call. He named six words that Democrats will use — “betrayal, abuse of power, national security” — as they make the case that Trump abused his office when he pressured Ukrainian President Volodymyr Zelensky to investigate Joe Biden and his son.

House Judiciary Chairman Jerry Nadler, whose panel will be responsible for crafting any articles of impeachment, endorsed the strategy as outlined by Pelosi.

“If we stick to the speaker’s plan, we will prevail,” Nadler said, according to a person on the call. A spokesman for Nadler confirmed that the chairman supports Pelosi’s approach.

House Democrats returned to their districts this weekend for a two-week recess, during which many will face pressure to carry the caucus’ message in the nascent stages of its impeachment inquiry.

Several freshman lawmakers from battleground districts asked Pelosi and other Democratic leaders before they left Washington for help handling their caucus’ impeachment message at home.

The DCCC poll, conducted Sept. 26-27, showed voters support a pro-impeachment Democrat over an anti-impeachment Republican by 11 percentage points.

INTERACTIVE: See where House lawmakers stand on impeachment

But Bustos cautioned that the DCCC poll reflected national support, not support from specific swing districts. She said members should deploy their own polls — with help from the campaign committee — and use existing field staff to focus their messaging.

A POLITICO/Morning Consult poll released last week also found that support for impeachment proceedings has risen since Pelosi announced plans to formalize the inquiry.

Pelosi, speaking this weekend in Texas, dismissed potential political consequences of impeachment.

“It doesn't matter,” Pelosi said in the wrap-up event of a Texas Tribune festival. “Our first responsibility is to the Constitution.”

On the call, Pelosi reiterated that Democrats would remain focused on their legislative agenda and said she hopes Trump doesn't walk away from a deal on trade or drug pricing — a dual approach that many moderates have said is key to keeping the House.

Lawmakers were also told on the conference call which committees will be handling which aspects of the investigation. The Intelligence Committee will focus on the substance of the president’s alleged actions as outlined in a whistleblower complaint that the Trump administration initially withheld from Congress, while the Foreign Affairs Committee plans to probe the details of the State Department’s possible involvement with Rudy Giuliani, Trump’s personal attorney.

The Oversight and Reform Committee, meanwhile, will look into the potential misuse of classification systems at the White House — an apparent reference to the whistleblower’s complaint, which alleged that White House officials sought to “lock down” the transcript of Trump’s phone call with Ukraine's president.

The Intelligence panel will reconvene in Washington this week despite the scheduled recess as it works to corroborate the whistleblower’s allegations. Rep. Adam Schiff (D-Calif.), the chairman of that panel, announced on Friday that the intelligence community’s inspector general, Michael Atkinson, will appear before the committee behind closed doors this coming Friday.

Appearing on ABC’s “This Week” on Sunday morning, Schiff said he expects the whistleblower to testify “very soon,” adding that he is waiting for acting Director of National Intelligence Joseph Maguire to grant security clearances to the whistleblower’s legal team, which is being led by Andrew Bakaj, a veteran national security attorney.

In a statement later Sunday, Bakaj and his co-counsel I. Charles McCullough said no date or time had been set but “discussions continue to occur to coordinate and finalize logistics.”

“Protecting the whistleblower’s identity is paramount,” Bakaj said.

Democrats are also seeking information from the Trump administration about crucial military aid to Ukraine that was put on hold earlier this year around the same time that Trump asked Zelensky to look into Biden and his son Hunter. On Friday, the chiefs of the House Appropriations and Budget committees demanded documents as they seek to find out “when, why, and how the president and [the Office of Management and Budget] withheld this funding.”

Some Democrats have suggested that Trump withheld the military aid in order to gain leverage over Zelensky, though there has been no clear link established between the aid and Trump’s July 25 phone call with Zelensky.

Heather Caygle contributed to this report.