(Bloomberg) -- Republican Donald Trump’s lead over President Joe Biden has grown to six points, according to two prominent national polls, intensifying pressure on the beleaguered Democratic incumbent to drop out.

A New York Times/Siena College poll released Wednesday found Trump ahead by 49% to 43%, while a Wall Street Journal poll found an almost identical result, with him leading by 48% to 42%. It’s Trump’s largest lead of the race in both polls. 

The surveys suggest that worries over Biden’s age are driving the shift. Nearly three-quarters of voters in the Times poll said the 81-year-old president is too old for the job — up 5 points from a pre-debate poll taken last week. And the Journal poll found that the share of voters who say Biden is too old to run has risen by 7 points since February, to 80%.

The onslaught of discouraging poll results comes as Biden’s campaign looks to tamp down a revolt among some Democratic lawmakers and donors urging him to stand aside and allow another candidate to take on Trump. Biden, the oldest president in US history, delivered a halting performance in last week’s debate, fueling worries that he is not unable to serve another four-year term.

In a memo to campaign staff earlier Wednesday, leaders on Biden’s team acknowledged they were likely to see “a larger swing in the race” in the Times survey, one of the most closely watched polls in US politics. 

“Polls are a snapshot in time and we should all expect them to continue to fluctuate — it will take a few weeks, not a few days, to get a full picture of the race,” campaign chair Jen O’Malley Dillon and campaign manager Julie Chavez Rodriguez said in the email.

Still, the trendline is largely backed up by a number of other national polls in the last week, with major polling averages moving consistently in Trump’s direction.

Those national numbers may understate Biden’s problems. Presidential elections are won in the Electoral College, and polls of battleground states show Trump increasing his average lead over the past week in Arizona, Georgia, Michigan, Nevada, North Carolina and Pennsylvania. Wisconsin remains the closest battleground, with Trump and Biden tied in the RealClearPolitics average.

Biden campaign pollster Molly Murphy said in a statement that the Times poll “doesn’t fundamentally change the course of the race.”

“President Biden continues to narrow Trump’s support among independents, and we have work to do to bring home our coalition — all the while Trump appears unable to expand his coalition,” she said.

The Times surveyed 1,532 registered voters from June 28 to July 2, with a margin of sampling error of 2.8 percentage points. The Journal poll surveyed 1,500 registered voters from June 29 through July 2, with a margin of error of 2.5 percentage points.

(Updates throughout with Wall Street Journal poll results.)

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