Hillary Clinton at an event in Akron, Ohio. Justin Sullivan/Getty Images The polling surge Hillary Clinton was expected to obtain after last week's presidential debate has arrived.

A series of new polls released this week suggest the Democratic nominee is increasing her national lead after a well-received first debate performance and a week of tough stories for her Republican opponent, Donald Trump.

A CBS poll released Tuesday found Clinton leading Trump by 4 points with 45% support nationally among likely voters, a 3-point swing from when a similar CBS poll was conducted in September. The same poll showed Libertarian presidential nominee Gary Johnson with 8% support and Green Party nominee Jill Stein with 3% support.

A CNN/ORC poll released Monday found Clinton in even better shape among likely voters nationally, with a 5-point lead over Trump in a four-way race. Similar YouGov/Economist and Morning Consult/Politico surveys of national voters taken after last week's debate also found Clinton with leads larger than the margins of error, despite Trump's lead in many national polls entering the debate.

The slew of surveys follow a week that found Trump's campaign on the defensive over numerous controversial comments and revelations.

The real-estate magnate spent the week repeatedly addressing the weight gain 20 years ago of Alicia Machado, the winner of the 1996 Miss Universe pageant whom Trump publicly asked to slim down. And on Saturday, a New York Times report revealed that the Republican presidential nominee reported in his 1995 tax returns a loss of over $900 million that may have allowed him to avoid paying federal income taxes for almost two decades.

Still, the appearance of volatility in the polls may be somewhat overstated.

Some experts including Sam Wang of Princeton University assert that the polling is actually as stable as in other years, largely because most likely voters have already chosen which party they will support.

"The polling data is surprisingly invariable," Wang told Business Insider after the first debate. "This year's election is as stable as four years ago in 2012, with Obama versus Romney, maybe even a little more stable."

He added: "Even though this year is weird, it probably reflects increasing voter polarization."