The Trump rally that has sent stocks almost 10% higher since the election, up to record highs, could be in jeopardy.

It’s been based largely on expectations for tax reform, deregulation and, to a lesser extent, a major infrastructure spending package, but now expectations for tax reform seem to be shifting.

“Tax reform could take 10 to 18 months to pass, with a growing risk that it won’t be as dramatic as advertised two months ago,” wrote Greg Valliere, chief global strategist at Horizon Investments in his latest Capital Notes.

The sticking point is a border adjustment tax, which would increase taxes on companies that import products such as retailers while cutting them for exporters, raising $1 trillion over 10 years. Major retailers like Target and Walmart, which import many goods, oppose this tax, and that’s complicating efforts to pass any tax measure, according to Valliere.

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“The specifics of tax policy are going to make a big difference,” says Hugh Johnson, chairman and chief investment officer of Hugh Johnson Advisors.

He foresees a struggle between those Republicans who want to offset tax cuts with revenue raisers such as the border tax and elimination of the corporate tax deduction for interest payments and those who aren’t as concerned about the offsets.

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Those offsets “really count,” says Johnson, so “nobody knows what the configuration of the tax cuts will be or the timing. … If there is no border adjustability tax there may be no tax cuts at all or not until 2018.”

Despite those concerns Johnson is maintaining his stock allocations, but not adding to them.

Mohammed El-Erian, chief economic advisor of Allianz and former CEO of PIMCO, sees a different tug-of-war affecting stocks, one between tax reform, infrastructure spending and deregulation, which offer the prospect of “healthy reflation” and policies such as trade protectionism that risk stagflation, according to a recent Bloomberg View post.

These opposing sets of “policy influencers … are much more tenuously balanced now,” wrote El-Erian, adding that “any particular policy move is likely to have a more marked price impact.”

He’s expecting a breakout to one side or the other and wrote that “a sustainable rise in stocks” will require a “detailed careful design and, with the administration working collaboratively with Congress, sound implementation.”

Nick Colas, Chief Market Strategist of ConvergEx Group, is less concerned about a Washington-related shock than the economy and Federal Reserve policy this year. “The market has priced in two rate hikes, but the Fed is still talking about three.”

Indeed, in her semiannual testimony to the two houses of Congress last week, Federal Reserve Board Chair Janet Yellen iterated the central bank’s December expectation for three rate increases in 2017, which would raise the federal funds benchmark rate from its current range or 0.5-0.75% to 1.25% to 1.5%.

“I don’t worry about tax bill being done in Q4 not Q3 and if it’s in 2018 that’s fine too,” says Colas. “Something will be done.”

Tom Howard, CEO and chief investment officer of AthenaInvest, an RIA that focuses on behavioral factors, is also optimistic about the stock market. “We’re very positive.”

All three behavioral currents that the firm focuses on are flashing green as is its measure of the economy. But Howard notes that one measure — broad behavioral current, which looks at forward price-to-earnings ratios — is the closest to yellow, a sign of caution.  “The median S&P 6,500 P/E multiple “is a little high.”

Johnson, too, says stocks are “modesty overvalued,” but he doesn’t expect the major indexes will retreat much from current levels unless Congress cuts back on fiscal stimulus — which includes tax cuts as well as additional spending — or the Fed continues to raise rates into 2018.

According to FactSet, the forward 12-month P/E ratio for the S&P 500, which stands at 17.6, based on the Feb. 16 closing price, has reached its highest level since 2004.

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