March 22 (Reuters) - From the basement to the third floor of Democratic Party headquarters in Washington, dozens of election campaign workers are glued to screens playing back videos of Donald Trump and other Republicans, digitally documenting their policy positions on everything from torture to climate change.

The newly bulked up operation, including research, of more than 70 people is central to the Democrats' strategy to sink whoever the Republicans nominate to run for the White House in the Nov. 8 U.S. presidential election....

The video clips will be used as grist for attack ads that will be deployed rapidly on social media sites any time Trump, or either of his rivals, U.S. Senator Ted Cruz of Texas and Ohio Governor John Kasich, strays during the general election campaign from policy proposals they touted in the nominating contests across the country.

That could, in theory, hinder them from appealing to the millions of more moderate voters needed to beat former Secretary of State Hillary Clinton or U.S. Senator Bernie Sanders of Vermont, the two competitors for the Democratic nomination....