Sarah Isgur is a CNN political analyst. She has worked on three Republican presidential campaigns and is an adjunct professor at George Washington University's School of Media and Public Affairs. She is a graduate of Harvard Law School. The views expressed here are hers. Read more opinion on CNN.

(CNN) Is it Groundhog Day all over again or could this time be different? After all, we've seen pundits clamor to tell us that Donald Trump is in trouble before. Actually, we've seen it quite a few times. But perhaps this is one time where television really fails to capture the true excitement of a large squirrel predicting the weather, right?

You may remember that the "Access Hollywood" recording of President Donald Trump was released on a Friday afternoon in October 2016. Many of us here in Washington were heading home after a long week. Phones started to buzz at every happy hour around town. Reporters dashed back to their bureaus. Within hours, Republicans around the country pulled their endorsements

Paul Ryan canceled a planned joint appearance with Trump the next day, noting the "elephant in the room." Pundits fell over themselves predicting the catastrophic polling fallout with voters that was surely imminent. (As just one example, in the days that followed, this analyst was quoted on the record as saying, "Look at Paul Ryan today: He is acknowledging what we all know, the race for the White House is over.")

But Republican voters disagreed. The polling meltdown never came. Paul Ryan was heckled by voters chanting Trump's name and screaming, "You turned your back on us."

And you know what happened next: The RNC predicted defeat , but Trump won the presidency anyway. Perhaps most tellingly, according to a CBS/YouGov poll , 91% of Trump's Ohio voters and 90% of his Pennsylvania voters said the tape didn't change at all how they viewed Trump.

The GOP establishment was chastened, happy to be back in power, and still unsure where their voters stood on the guy they had just put behind the Resolute Desk.

Fast forward a year and the same thing happened around the Mueller investigation : GOP senators were initially eager to jump on board with the appointment of a special counsel to look into the allegations of Russian interference and obstruction by the President, Republican voters turned against it and Trump's Twitter account has more followers than ever. Those that couldn't or wouldn't get on board with the new Republican reality showed themselves out ahead of the 2018 midterms.

Lesson learned, right? Maybe the President is right that he could "stand in the middle of Fifth Avenue and shoot somebody" and not lose any support with Republican voters, as he claimed on the campaign trail in January 2016.

How, then, do we explain why the exact opposite is happening in the polls this week?

While the Republicans left in Congress are trying to stay out of it , Republican voters aren't as quick to dismiss the whistleblower's allegations as they were to move on from the Mueller Report or the "Access Hollywood" tape. Nearly 1 in 4 such voters approve of House Democrats' impeachment inquiry, per a CBS News poll. And almost half of GOP voters either want to "wait and see the facts" or already think Trump has done something wrong.

Most surprisingly, support impeachment has risen 8% among Republicans since May, according to a new poll from CNN. That may sound like small potatoes, but remember that support for removing Nixon among Republican voters -- during a far less polarized time and without cable news relentlessly circulating each side's talking points -- topped out at 31%.

Interestingly, according to an NPR/PBS NewsHour/Marist poll, 80% of Republican voters are paying very close or fairly close attention to the news about the House impeachment inquiry -- higher than Democrats (70%) or Independents (64%).

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Can House Speaker Nancy Pelosi win over House and Senate Republicans on impeachment by convincing them that Trump is vulnerable this time? Probably not -- but she doesn't need to. She just needs to crack the Republican voter firewall enough to convince Republicans in the Senate that this isn't "Access Hollywood" all over again.

And in the meantime, the President needs to assure his voters, weary of defending him, that the Democratic Lilliputians -- for all their endless efforts -- will never succeed in restraining him.