With Republicans in control of the White House and both chambers of Congress, Obamacare repeal was supposed to be a slam dunk. Just ask former CIA director George Tenet what he thinks of "slam dunks." Sometimes, they don't happen.

In the week ahead, as the GOP civil war worsens, investors should assume nothing. Financial deregulation, the defense and infrastructure build-ups--even tax cuts--are in jeopardy. Below is a guide to the landmines ahead and how to sidestep them.

In another one of his manic tweetstorms on March 30, Donald Trump blamed Democrats and the GOP's ultra-right Freedom Caucus in the House for torpedoing his health care initiative. Caucus members who didn't get in line with his agenda, the president thundered, would encounter his opposition in the 2018 midterms.

Mindful that Trump's approval rating sits at a dismally low 35%, the caucus not only dismissed Trump's threats but also mocked them. Quick perspective: During the Watergate hearings in May 1973, President Nixon's approval rating was actually higher at 36%.

Making it even tougher for the ruling party to govern is the Trump-Russia scandal, which intensifies with each passing day. Democrats smell blood, and Wall Street senses trouble.

To be sure, the S&P 500 closed on Friday with a gain of 0.8% for the week. The benchmark index racked up a robust first quarter, with an increase of 5.5%, which was surpassed by an even stronger performance by the Nasdaq.

The technology-heavy Nasdaq gained 1.4% for the week, stretching its first-quarter gain to 9.8%. Tech stocks have been the real stars of the first quarter, and their momentum should continue, as economic expansion remains on track and IT capital spending grows. Year to date, sector bellwether Apple (AAPL - Get Report) has gained 24.04%.

But any crumb of bad news could send this overvalued market reeling, as we saw during the week of March 20, when over those five days the S&P 500 fell 1.4% amid Capitol Hill's health-care donnybrook.

In the week ahead, keep an eye on aerospace/defense companies, which have been rising on Trump's vows to beef-up defense. Since Nov. 9, industry stalwart Boeing (BA - Get Report) has gained 21.90%. But even the promised defense spending boom looks less likely to happen as time goes by.

For starters, Trump's proposed budget would need to get 60 Senate votes because it violates the Budget Control Act (BCA). Given that Trump's budget pays for a defense increase by gutting domestic programs cherished by Democrats, it's unlikely to get 60 votes. Even some conservative Republicans don't like Trump's proposed budget because they view it as profligate.

Exacerbating tensions in Congress is the hard-line stance of Mick Mulvaney, director of the Office of Management and Budget. As a Tea Party fiscal hawk, Mulvaney opposes funding defense procurement through the off-budget Overseas Contingency Operations account, which is the only way to get around BCA caps.

Meanwhile, the collapse of Trumpcare on March 24 has challenged the narrative of Trump as a master dealmaker. The president blustered into office with an ambitious plan to hike defense spending by $54 billion, by slashing an equal amount from domestic programs that enjoy entrenched constituencies. That's a recipe for political conflict.

That said, aerospace/defense should continue to thrive under Trump because the Pentagon usually gets its way no matter who occupies the Oval Office. Despite demagogic assertions to the contrary, defense spending was healthy under President Obama and it is likely to remain so. But don't assume the funding largesse will extend to all defense companies.

The upshot for investors: Instead of making broad generalizations about defense, infrastructure, taxes, and deregulation, you need to emphasize careful stock picking. That's why earnings reports and economic data carry particular weight right now.

In the week ahead, the key earnings reports to watch include Monsanto (MON) , Walgreens Boots Alliance (WBA - Get Report) , and Bed Bath & Beyond (BBBY - Get Report) (Wednesday); and Constellation Brands (STZ - Get Report) and PriceSmart (PSMT - Get Report) (Thursday).

Important economic reports on the docket: PMI Manufacturing Index, Construction Spending, Gallup U.S. Consumer Spending Measure (Monday); Motor Vehicle Sales, Factory Orders (Tuesday); ADP Employment Report, Gallup U.S. Job Creation Index, PMI Services Index (Wednesday); Chain Store Sales, Jobless Claims (Thursday); Baker Hughes (BHI) Rig Count (Friday).

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John Persinos is an analyst with Investing Daily. At the time of publication, Persinos owned stock in Apple and Boeing.

Action Alerts PLUS, which Cramer manages as a charitable trust, is long WBA and AAPL.