Wherever you turn, stocks are setting new records. On Wednesday, the Dow Jones Industrial Average closed above 21,000 for the first time in history. The previous day, the Dow ended a record-setting 12-day winning streak.

On Wednesday, the S&P 500 index SPX, -0.46% hit another milestone, reaching the 2,400 mark in intraday trading. The S&P already has topped many Wall Street strategists’ predictions for 2017, and some are scrambling to revise their targets higher. The Dow DJIA, +0.13% has tacked on nearly 2,800 points and the S&P has rallied 11% since Election Day. Snap Inc.’s SNAP, +1.59% successful initial public offering, in which the shares closed up 44% on their first day of trading, was the rally’s exclamation point.

We all know why that’s happened: Investors expect the Trump administration and Congress to slash regulations, cut taxes and perhaps enact a big infrastructure-building plan. That’s added fuel to an already growing economy and lifted business and consumer confidence. It’s also boosted the confidence of individual investors, who had sat out much of the eight-year-old bull market.

Wall Street led the charge early on, but now retail investors are back in force. On Saturday, The Wall Street Journal reported that individual investors are snapping up stock exchange-traded funds “at a record-breaking pace,” pouring around $124 billion into ETFs so far this year. Retail investors accounted for 85% of the inflows into BlackRock’s iShares ETFs. “The retail investor is leading the way this year,” a BlackRock official told the Journal.

And though no one states their political preferences when buying ETFs (thank God!), I’ll bet Republicans and Trump supporters, many of whom shied away from stocks during the “Obama bull market” that took the Dow from just under 8,000 to almost 20,000, are now jumping in with both feet.

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This column first highlighted the trend late last year. Three polls taken back in December bear it out:

•The CNBC All-America Economic Survey indicated that 42% of Americans expected the economy to improve in 2017, a substantial jump and the highest percentage of optimists since 2008. That, however, was “powered by Republicans and independents,” CNBC’s Steve Liesman reported. Some 74% of Republicans said the economy would improve in 2017, compared with only 15% the previous year. Republicans also “grew significantly more optimistic” on the stock market, Liesman wrote.

•A Bloomberg National Poll found 54% of Americans were bullish on the U.S. stock market for 2017. “More than three-quarters of those who voted for Trump say U.S. equities will be at higher levels at the end of 2017, while only about a third of those who voted for Clinton think so,” Bloomberg reported.

•The Wells Fargo/Gallup Investor and Retirement Optimism Index hit +96 in the fourth quarter, its highest point since January 2007. “Investor confidence zoomed 155 points in the post-election poll among investors who identify as Republican, from an index score of 0 in the third quarter,” according to Gallup. That’s zero, folks, with an “o.” “Conversely, Democrats’ confidence fell by nearly as much, from +174 to +25.”

Ladies and gentlemen of the jury, I rest my case.

Many conservatives and Republicans have avoided stocks for years, worried about the debt, the Federal Reserve’s “money printing,” the dollar as “fiat money,” etc., etc.

“For the past eight years, questions about how the economy is doing have been driven by partisan views. Republicans were all but in denial about job growth and improvement in the stock market,” pollster J. Ann Selzer told Bloomberg.

Instead, they kept their money in banks or their mattresses or took much too seriously the ads for precious metals on conservative talk radio. This doom-and-gloom investing had a huge opportunity cost: While cash earned nothing and gold was mired in a secular bear market, stocks gained around 150% during the Obama years, replenishing retirement accounts and then some. Fidelity’s 401(k) balances, for example, are at record levels.

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According to the Federal Reserve, Americans held $11.3 trillion in savings and checking accounts as of the third quarter of 2016. The Investment Company Institute reported that as of March 1, retail investors had nearly $1 trillion in money-market funds.

That’s a lot of cash that could be put to work. I’m still bullish on stocks and the economy, but risk is rising that ebullient investors will be disappointed if President Trump’s agenda gets stalled in Congress or if his administration gets hopelessly bogged down in Russia-related investigations and tweet storms.

Conservatives and Republicans are finally going all-in on a market they boycotted during the Obama years. That has added fuel to the rally’s fire. But it may eventually push this bull market into its final euphoric stage, when the greater fools finally come off the sidelines just in time to get their clocks cleaned.

Howard R. Gold is a MarketWatch columnist and founder and editor of GoldenEgg Investing, which offers exclusive market commentary and simple, low-cost, low-risk retirement investing plans. Follow him on Twitter @howardrgold.