The US House of Representatives narrowly passed the landmark healthcare reform bill earlier this week, with no Republican backing, after hours of fierce argument and debate.
The act, at the heart of President Barack Obama's political agenda, extends coverage to 32 million more Americans, and marks the biggest change to the US healthcare system in decades.
Republicans say the measures are unaffordable and represent a government takeover of the health industry.
Mrs Palin, a former vice-presidential candidate and ex-governor of Alaska, came to Nevada a day after leading a rally in Arizona in support of her 2008 presidential running mate, John McCain, who is facing a stiff challenge from a conservative Republican in his bid for a fifth term in the Senate.
This election will be decided by Nevadans, not people from other states who parachuted in for one day to have a tea party
Senator Harry Reid
Standing on a wind-whipped makeshift stage outside the desert town of 1,000, she told the cheering crowd that Senator Reid was "gambling away" Americans' future.
"Someone needs to tell him, this is not a crapshoot [a gambling game played with dice]," she said.
The big-government, big-debt spending spree of Mr Reid, Mr Obama and House Speaker Nancy Pelosi was over, she said, adding: "You're fired!"
A string of opinion polls have suggested that Mr Reid is vulnerable in politically moderate Nevada after pushing Mr Obama's agenda in Congress, the Associated Press news agency reports.
His standing has also been hurt by Nevada's high unemployment and other economic woes.
In a statement released on Saturday, Mr Reid took a sarcastic tone: "I'm happy so many people came to see my hometown of Searchlight and spend their out-of-state money, especially in these tough economic times."
He added: "This election will be decided by Nevadans, not people from other states who parachuted in for one day to have a tea party."
The bus tour will take in 42 cities and is due to end in Washington on 15 April, the deadline for filing federal tax returns.
The Tea Party movement takes its name from the Boston Tea Party of 1773, when colonists dumped tea off English ships to protest what they considered unfair taxation by the British.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.