(KTVU) - The presidential primary race turns to Wisconsin Tuesday where the officials are predicting the highest voter turnout for a primary in decades.
Polls suggest that the second place candidates in both the Democrat and Republican parties are expected to win in Wisconsin.
In the Republican race, the RealClearPolitics average of recent polls shows Ted Cruz leading with 39 percent, Donald Trump with nearly 35 percent, and John Kasich with 19 percent.
In the Democratic race, the RealClearPolitics average has Bernie Sanders ahead with almost 48 percent and Hillary Clinton with about 45 percent.
Experts say Wisconsin is critical because it's seen as a bell-weather state.
Even though it's across the country, Bay Area activists have been busy calling Wisconsin voters for their candidates.
At one phone bank in Oakland, volunteers were placing calls for the Bernie Sanders campaign. Many California voters realize that if the races remain close, the decision for both parties could come down to California's primary in June.
"It's really important for California to work for Wisconsin, Wyoming, New York, Pennsylvania because they'll bring it home," said Cheri Johansen, an Alameda volunteer.
"I've been watching every primary. I know exactly what's going on. I've been calling for a while, since way before Washington, Idaho, Utah, I've been at this for a while," said Viveca Bradley of Oakland.
Sanders campaigned in Wisconsin on the eve of the primary. His call for a $15 minimum wage and his support for labor unions has attracted followers there, where Republican governor Scott Walker has clashed with unions.
Clinton campaigned in New York, deciding to look ahead to the delegate-rich state where she's leading Sanders right now in polls. Clinton and Sanders have agreed to meet for a debate April 14th, just five days before the New York primary.
"The question is can Bernie Sanders who's won about six of the last eight caucus contests, translate this into support and the notion that he's still winning and contesting with her," said James Taylor, a professor of politics at the University of San Francisco.
In the Republican race, Ted Cruz said Monday that the Republican nomination should go to either him or the current frontrunner Donald Trump, not to John Kasich who remains trailing behind.
Donald Trump who also campaigned in Wisconsin said he feels he will win the state. Some experts, however, say Trump might start seeing the impact at the polls of recent comments about criminalizing women who get abortions if abortion was made illegal.
"Wisconsin does have the electoral elements that Cruz nees to be successful and he probably will win by default. I think what we are seeing the beginning of a Donald Trump fatigue," said Professor Taylor.
Both Cruz and Trump have tried to sideline Kasich who claims he would be a better candidate in a general election and says he could have a chance to capture the Republican nomination if no one gets enough votes in a contested Republican convention.
For Republicans, 42 Wisconsin delegates are at stake Tuesday.
For Democrats, 96 delegates are up for grabs in Wisconsin.
Polls close at 6 p.m. PST.