WASHINGTON (AP) — Republican Leader Mitch McConnell said Monday that Senate rules would require him to take up any articles of impeachment against President Donald Trump if approved by the House, swatting down talk that that the GOP-controlled chamber could dodge the matter entirely.

"I would have no choice but to take it up," McConnell said on CNBC. But he cautioned, "How long you're on it is a whole different matter."

House Democrats are pushing for quick action on their probe into a phone transcript and whistleblower complaint that Trump pressured Ukraine's president to investigate Democratic foe Joe Biden's family. If the House approves articles of impeachment — not introduced at this point — they would be sent to the Senate for trial. McConnell suggested he does not have the 67 votes to change the rules. But the Kentucky Republican, the Senate's chief strategist, left open what he means by taking up the issue.

Those tricky procedural questions could affect Trump's political future and next year's presidential and congressional election.

As Trump raged on Twitter on Monday, the House plowed ahead with formal impeachment proceedings into whether the president pressured the leader of an Eastern European country to investigate former Vice President Biden and his son.

Democrats are driving the proceedings toward what some hope is a vote to impeach, or indict, Trump by year's end, and they have launched a coordinated political, messaging and polling strategy aimed at keeping any backlash in closely divided districts from toppling their House majority.

House intelligence committee chairman Adam Schiff is expected to issue new subpoenas, depose witnesses and perhaps hold a hearing as soon as this week. He said on Sunday that the panel would hear from the still-secret whistleblower "very soon," but that no date had been set and other details remained to be worked out.

Polling showed some movement in public sentiment.  A one-day NPR/PBS NewsHour/Marist poll conducted Sept. 25 found that about half of Americans — 49% — approve of the House formally starting an impeachment inquiry into Trump.

There remains a stark partisan divide on the issue, with 88% of Democrats approving and 93% of Republicans disapproving of the inquiry. But the findings suggest movement: Earlier polls conducted throughout Trump's presidency have consistently found a majority saying he should not be impeached.

The sometimes-confusing challenge of defending Trump broke into the open on Sunday's talk shows. Rudy Giuliani, the president's lawyer, insisted the real story is a conspiracy theory that has been debunked. Stephen Miller, Trump's senior policy adviser, blamed a "deep state" of Democrats within the government. And Rep. Jim Jordan of Ohio pointed at Biden's son.

But the real question for Republicans is what happens if the House votes to impeach Trump and sends the issue to the Senate for trial.

A memorandum that Senate Republicans circulated over the weekend acknowledged it would be hard for McConnell to "bar the doors" and prevent the resolution managers from presenting the articles to the Senate. After that, though, McConnell has procedural options, including limiting the time they could be considered.

"How long you're on it is a whole different matter," he said, without elaborating.

Republicans, meanwhile were split over how and whether to defend Trump's own words contained in a phone transcript and his actions, described by a whistleblower's report — both of which were made public by the White House.

The result has been a rainbow of approaches, led by Trump, who stormed on Twitter that the whistleblower was "fake" and suggested the people leading the probe should be arrested and charged with treason.

"The Fake Whistleblower complaint is not holding up," he tweeted Monday morning.

"I am deeply frustrated with what he and the legal team is doing and repeating that debunked theory to the president. It sticks in his mind when he hears it over and over again," said Tom Bossert, Trump's former homeland security adviser. "That conspiracy theory has got to go, they have to stop with that, it cannot continue to be repeated."

Not only did Giuliani repeat it Sunday, he brandished pieces of paper he said were affidavits supporting his story.

"Tom Bossert doesn't know what's he's talking about," Guiliani said. He added that Trump was framed by the Democrats.

Senior White House policy adviser Stephen Miller, meanwhile, noted that he's worked in the federal government "for nearly three years."

"I know the difference between whistleblower and a deep state operative," Miller said. "This is a deep state operative, pure and simple."

Meanwhile, Rep. Jim Jordan, R-Ohio, heatedly said Trump was merely asking Ukrainian President Volodymyr Zelenskiy to root out corruption. That, Jordan said, includes Hunter Biden's membership on the board of a Ukrainian gas company at the same time his father was leading the Obama administration's diplomatic dealings with Kyiv. There has been no evidence of wrongdoing by either of the Bidens.

Trump has insisted his call was "perfect."

"He didn't even know that it was wrong," said House Speaker Nancy Pelosi, describing her own phone call from Trump in which the president suggested the documents would exonerate him.

Bossert, an alumnus of Republican George W. Bush's administration, offered a theory and some advice to Trump: Move past the fury over the 2016 Russia investigation, in which special counsel Robert Mueller found no evidence of conspiracy but plenty of examples of Trump's obstruction.

"I honestly believe this president has not gotten his pound of flesh yet from past grievances on the 2016 investigation," Bossert said. "If he continues to focus on that white whale, it's going to bring him down."

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Giuliani appeared on ABC's "This Week" and CBS' "Face the Nation," while Schiff was interviewed on ABC and NBC's "Meet the Press." Bossert spoke on ABC and Miller on "Fox News Sunday." Jordan appeared on CNN's "State of the Union." Pelosi and McCarthy appeared on CBS' "60 Minutes."

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Associated Press writers Kevin Freking, Eric Tucker and Mary Clare Jalonick in Washington and Bill Barrow in Atlanta, and AP Polling Director Emily Swanson contributed to this report.

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