Washington (CNN) First, President Donald Trump said he would take responsibility for any potential government shutdown . Later, as the partial shutdown got underway, it was top Senate Democrat Chuck Schumer's fault. Then Trump placed the blame on top House Democrat and now House Speaker Nancy Pelosi.

Now? It's the fault of all the Democrats running to replace him in 2020.

Thirteen days in, the President and Democrats remain at odds over funding for a US-Mexico border wall, which has stymied negotiations on passing the funding broader measures needed to reopen the government.

Trump initially said he would "take the mantle" of blame for a shutdown due to border security disagreements, but ahead of Democrats' takeover of the House of Representatives on Thursday, he's sought to shift the blame onto the Democrats' future political ambitions.

The Shutdown is only because of the 2020 Presidential Election. The Democrats know they can't win based on all of the achievements of "Trump," so they are going all out on the desperately needed Wall and Border Security - and Presidential Harassment. For them, strictly politics!

"The Shutdown is only because of the 2020 Presidential Election," Trump tweeted Thursday. "The Democrats know they can't win based on all of the achievements of 'Trump,' so they are going all out on the desperately needed Wall and Border Security - and Presidential Harassment. For them, strictly politics!"

Here's a rundown of the shifting list of who Trump says to blame for the shutdown:

Trump says he'll own the shutdown

JUST WATCHED Trump: I don't mind owning shutdown Replay More Videos ... MUST WATCH Trump: I don't mind owning shutdown 01:13

In the now-infamous December 11, post-midterm-election Oval Office meeting with Pelosi and Schumer, Trump invited in news cameras and then insisted he would be "proud" to shut down the government over border security and wall funding.

"I'll tell you what, I am proud to shut down the government for border security, Chuck," Trump said "So I will take the mantle. I will be the one to shut it down. I'm not going to blame you for it."

But on Thursday, top White House adviser Kellyanne Conway said Trump won't own it anymore.

Asked if Trump regrets saying he'd take ownership of the shutdown, Conway said: "He doesn't own the shutdown any longer."

"The (Republican-led) House passed a $5.6 billion border security funding ... and now the Senate has to do its job." Conway said, referencing a short-term spending bill on border security that House Republicans passed during the previous Congress but was never voted on by the Senate.

Trump says the shutdown is Schumer's fault

JUST WATCHED Schumer: GOP using shutdown as hostage Replay More Videos ... MUST WATCH Schumer: GOP using shutdown as hostage 02:19

By December 30, about a week into the partial shutdown, Trump sought to blame Schumer.

Great work by my Administration over the holidays to save Coast Guard pay during this #SchumerShutdown. No thanks to the Democrats who left town and are not concerned about the safety and security of Americans! — Donald J. Trump (@realDonaldTrump) December 30, 2018

"Great work by my Administration over the holidays to save Coast Guard pay during this #SchumerShutdown. No thanks to the Democrats who left town and are not concerned about the safety and security of Americans!" Trump tweeted

Trump's tweet apparently tries to refute Schumer and Pelosi's Oval Office reference to a potential shutdown as a "Trump shutdown" by labeling it a "#SchumerShutdown."

At that time, Republicans still controlled the House, but in order to reopen the government, Senate Democratic votes were needed -- making it, in Trump's mind, a Schumer shutdown.

Trump, White House officials blame Pelosi

JUST WATCHED Fact check: Trump's heated Oval Office meeting Replay More Videos ... MUST WATCH Fact check: Trump's heated Oval Office meeting 04:59

More recently, White House officials moved to point fingers at Pelosi for the shutdown, suggesting she had to protect her chances of winning the House speakership by opposing the wall to appease liberals in her base.

That logic flies in the face of Pelosi's staunch opposition to the increase in border funding.

Trump first made the argument in early December, tweeting ahead of his Oval Office meeting with Pelosi and Schumer: "They will fight it at all cost, and Nancy must get votes for Speaker."

Then, in late December, following the start of the shutdown, other administration officials took up the claim.

Acting chief of staff Mick Mulvaney told Fox News that Pelosi "cannot be seen by her party as being weak on negotiating with Donald Trump."

Similarly, White House press secretary Sarah Sanders said: "Pelosi is only looking to protect her speakership and not protect our borders."

"And that's why she's unwilling to negotiate with us and unwilling to make any type of deal," Sanders added.

Trump blames the political ambitions of Democrats in 2020

JUST WATCHED Graham: If Trump caves, it's end of presidency Replay More Videos ... MUST WATCH Graham: If Trump caves, it's end of presidency 00:40

Then, during Wednesday's nearly two-hour, partially televised Cabinet meeting, Trump said the federal government is "in the shutdown because of the fact that the Democrats are looking to 2020."

"They think they're not going to win the election," he said. "I guess a lot of signs point to the fact that they're not going to win the election. And I hope they're not going to win the election. But they view this as an election point for them."

Trump, who launched his 2016 presidential debate decrying illegal immigration, claimed Wednesday he's not thinking about the politics of the debate.

"I actually think it's bad politics, but I'm not thinking about the politics. I'm thinking about what's right and what's wrong. And we need a physical barrier," he said.

But behind closed doors, Trump admitted he is acutely aware of the politics of the debate.