State of 2016 play: Iowa caucuses will provide answers

DES MOINES, Iowa (AP) — Only a week remains before the Iowa caucuses, the first contest in a tumultuous presidential campaign that has challenged long-held political assumptions.

While some party leaders are coming to grips with the prospect of Trump as the nominee, a group of more mainstream candidates is battling to beat expectations in Iowa, head into the New Hampshire primary on Feb. 9 with momentum and rise to challenge the front-running billionaire.

The Democratic race has evolved into a surprisingly heated contest between Hillary Clinton and Vermont Sen. Bernie Sanders, the self-described democratic socialist who has energized young voters and liberals.

Many professional Republicans distain Trump and worry about his long-term effect on the party's ability to win over general election voters.

[...] his momentum has stalled as high-profile conservatives defected to Trump and Cruz's rise drew stiff opposition from mainstream Republicans.

Cruz has a well-tended network of grassroots conservative supporters across the state.

The fear was that any harsh critique of the liberal senator who was pushing a "political revolution" might alienate his supporters, so important to the Democratic nominee in the general election.

In the past week, Clinton went after Sanders' foreign policy credentials, his health care proposal and his plans to crack down on Wall Street.

Clinton's allies point out that an ad released by the Sanders campaign, an uplifting montage of Americana set to a Simon and Garfunkel tune, featured mainly white people, and they are casting it as a sign of the senator's disrespect for minorities.

The group is identifying voters by phone, online and social media and using the connections to help turn out Rubio supporters.

Party loyalists tend to dominate the Iowa caucuses, but an influx of independent and young voters can create a winning formula.

"More than any other candidate, Trump's success will hinge on his ability to expand the Iowa caucus electorate by turning out independents and first-time caucus attendees," said former Iowa GOP Chairman Matt Strawn.