CNN  — 

Poll of the week: A new national Monmouth University poll finds that former Vice President Joe Biden leads President Donald Trump by a 52% to 41% margin.

Biden’s advantage is confirmed by an NBC News/Wall Street Journal poll out Sunday morning putting Biden at 49% to Trump’s 42%.

Both polls show Trump with a substantial lead among self-identified Republicans: 93% to Biden’s 5% (Monmouth) and 92% to 4% (NBC News/Wall Street Journal).

What’s the point: Trump has made a clear play during his presidency of satisfying the Republican base, and the polling indicates that this effort is clearly paying off. His base is not abandoning him, even as his overall numbers remain weak.

Trump’s problem is that he’s pretty much tapped out this reservoir of support.

View Trump and Biden head-to-head polling

After making a great effort to run up the score in the primaries against basically no competition, Trump’s winning a little less than 95% of the Republican primary vote overall. That looks a lot like the polling for the general election putting him at a little less than 95% of the Republican vote. It’s going to be difficult for him to get much beyond that.

Indeed, Trump has higher support among Republican voters right now than any Republican since at least 2000. You can see this in the ABC News/Washington Post poll. That one, like Monmouth’s and NBC/Wall Street Journal’s, has Trump nearly to 95% (at 94%), while Biden lingers at a mere 4%.

Dating back to 2000, no Republican ever had more than 91% of Republicans backing him at this point in ABC News/Washington Post polling. The average Republican had 84% of Republicans behind him. A base-first strategy in those elections made a lot more sense than one during the Trump era.

(The historic nature of these numbers holds if we include independents who lean Republican.)

Perhaps Trump believes he doesn’t need to change his strategies because he disregarded most people’s advice and still won in 2016. That’s a mistake. Beyond the fact that there’s good evidence that Trump ran as much more of a moderate than he’s governed, Trump had a lot more room to grow with the base in 2016. He scored just 74% of self-identified Republicans in an ABC News/Washington Poll taken right around this point – the lowest of any Republican since 2000.

Where Trump is weak is outside the Republican base. In the ABC/Washington Post (the numbers are similar for Monmouth and NBC News/Wall Street Journal), Trump’s at 39% among independents and 3% among Democrats. Both of those are lower than any Republican at this point in ABC News/Washington Post polling dating back to 2000.

There is, in other words, a lot more potential support for Trump outside the core Republican base. Trump, though, doesn’t seem interested in making the effort.

If Trump doesn’t switch things up, he may find that the other side’s base is bigger than his. Biden is winning a larger share of Democrats in an average of live interview polls (including an NPR/PBS News Hour/Marist College poll) out this week (94%) than Trump is winning Republicans (92%). The average poll, as has been true for almost every year on record, measured more Democrats than Republicans in this country.

By continuing his base-first strategy, Trump ensures that he won’t see the bottom fall out. He will find, however, that actually accumulating the coalition needed to win will be exceeding difficult.

This story has been updated to include results from an NBC News/Wall Street Journal poll out Sunday.