Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a columnist at Newsday since 2007.

A telling moment arrived for the national Democrats over the weekend when former President Bill Clinton and academic-activist Cornel West traded verbal shots from a distance regarding the Bernie Sanders campaign.

Sanders backers heckled Clinton as he campaigned for his spouse in East Los Angeles. The aspiring first husband taunted back: “If I were them, I’d be screaming too, because they know they will be toast by Election Day.”

West, introducing Sanders at a San Diego rally, called the Clinton “toast” remark arrogant and vindictive.

“What is he talking about?” demanded West — who previously compared Hillary Clinton to the lip-syncing singing group Milli Vanilli.

If the Vermont senator indeed proves to be “toast,” it ironically turns the major party nominees into a study in contrasts. Newly minted Republican Donald Trump will have carried out a party coup, while entrenched Democrat Hillary Clinton will have survived one.

Trump in the primaries defeated prominent “establishment” figures, including the twice-in-the-White House Bush family. Along the way, Trump trashed mainstream party positions. He denounced the Iraq War effort, vowed to protect Social Security, talked about a “workers’ party,” and slammed GOP-backed trade deals.

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For the Democrats, it was Sanders who led a rebellion against the party’s upper echelon. He attacked influential financial institutions, corporate trade deals, foreign entanglements and privileged tax arrangements.

If Clinton gets to carry her party’s banner while Trump secures the GOP position, both will face internal problems, but of a very different nature.

Clinton’s challenge: win over young voters, activists and labor unions that embraced Sanders’ populism — while retaining African-American support and institutional alliances.

Trump’s challenge: deploy fundraisers, operatives and permanent Washington types whom he reviled during primaries while keeping his bloc of white voters interested.

By locking up the nomination well ahead of the GOP convention, Trump got a head start in trying to take over the GOP and commence the general election race. His success has been mixed at best. Several well-known Republicans who endorsed him are still publicly criticizing Trump’s demeanor.

The next few months will test how far Republicans will go to beat Clinton.

If Clinton prevails as expected against Sanders, it remains to be seen how she will fare with her own party’s dissidents — and whether a fear of Trump is perhaps enough to carry the day for her party.

The next few months will test how far Democrats, in turn, will go to beat Trump.