Under the shadow of tomorrow's presidential primary, there's another very big race with national implications taking place in Oregon: The Dem Senate primary, where two candidates are locked in a brutal struggle for the right to take on vulnerable GOP Senator Gordon Smith.

The outcome tomorrow could determine whether Democrats have a chance at winning a big Senate seat that national strategists would absolutely love to capture -- and one that they think could be winnable, in a state that hasn't gone Republican since 1984 and where Barack Obama has led John McCain by double-digit margins.

What has national Dems on the edge of their seats is the fact that the candidate preferred by the national party -- state House Speaker Jeff Merkley -- might not prevail against his spirited primary challenger. Merkley is also under sustained attack from GOP incumbent Smith, who's launched an almost-unprecedented pre-primary ad campaign against him -- prompting some to charge that Smith is trying to swing the race to his lesser-funded opponent.

The guy who just might beat Merkley is attorney Steve Novick. An unorthodox candidate by any measure, he has become a surprise YouTube hit for his ad where he opens a beer with his prosthetic hook. Surprisingly, Novick has managed to lead Merkley by narrow margins in most polls.

National Dems are paying close attention to the race because of Smith's vulnerabilities. A conservative who has turned against the Bush Administration on many Iraq-related votes, Dems think they can hit Smith for the big period of time before he switched on the war, and on all the other economic issues where he still votes with the White House.

The national party backs Merkley because of his experience as a state legislator, and he's attracted the support of most unions and national donors, as well as most of the Oregon Democratic establishment. However, Novick has been able to depict Merkley as being too much of an establishment, machine-backed candidate, in a year when many Dem voters have wanted precisely the opposite of the usual politician.

Merkley has seized on the fact that Smith has been running attack ads against him on both TV and radio, charing that Smith is trying to engineer a win for the opponent he thinks would be more beatable: Novick.

Smith spokesperson R.C. Hammond says this is nonsense. He claims it was Merkley who started the attacks, with an ad contrasting his blue-collar background against Smith, who is a scion of the Udall political family. "He has no preference in the Democratic primary, he's leaving that decision to Oregon Democrats," Hammond said.

Merkley spokesman Matt Canter's answer: "That's a lame excuse for what they're actually doing, which is spending a half million dollars trying to swing the primary to the weaker Democrat."

Novick campaign manager Jake Wiegler, unsurprisingly, doesn't buy that theory. "I could see it as being an attempt to help Steve Novick," Wiegler said, "but I could also see it as an attempt to help Jeff Merkley by getting Democrats to rally around him."

The polls close tomorrow at 11 p.m. ET.