Boeing is on track for its worst week in two years, and with so much political uncertainty surrounding trade policy, more pain could be ahead, according to one long-time market watcher.

"The question is really not economic. It's political at this point," Boris Schlossberg, managing director of FX strategy at BK Asset Management, said on CNBC's "Trading Nation" on Wednesday.

Boeing shares have been weighed down by a potential trade war between President Donald Trump and China. A proposed trade package imposing tariffs on $60 billion worth of China-made goods could spark retaliation from the world's second-largest economy.

"Boeing does business with a lot of governments across the world, and if the U.S. policy now is going to be combative instead of conciliatory against everybody in the world, it's going to make Boeing's business much more difficult," said Schlossberg.

The largest aerospace company in the U.S. announced last year a $37 billion order for planes from China and the potential for $1 trillion worth of aircraft over the next two decades. More than half of its total sales come from outside the U.S.

The Chicago-based company's stock has lost more than 9 percent since tariff talk surfaced this month. Those losses have intensified this week with shares briefly falling into a correction on Wednesday. Its stock ended the session down 8 percent from a 52-week high set earlier in March, close to the 10 percent threshold indicative of a correction.

"I would stand aside for now until I see how policy checks out because it could get very ugly, very fast," warned Schlossberg.

Boeing's tailspin this week also spells trouble for the Dow, he added.

"Boeing is one of the most expensive components of the Dow so if it goes, the Dow goes," he said.

Its shares dragged the blue-chip index below 25,000 again on Wednesday after recovering that level last week. However, Boeing remains among the top performers this year. It has led the Dow over the past 12 months with gains of nearly 85 percent.

Boeing's days-long sell-off has it teetering on a critical support level, says Craig Johnson, chief market technician at Piper Jaffray.

"The technical picture isn't very rosy," Johnson told "Trading Nation" on Wednesday. "This is a stock that had gone parabolic, meaning it's gone up too far, too fast."

Its shares broke below their 50-day moving average on Tuesday, a level it had not fallen below since May. Its 200-day moving average, around $270, should provide its next critical support level, says Johnson, though downward pressure puts that level at risk.

"Most parabolic advances typically correct almost 100 to 110 percent of the advance. So be careful," Johnson warned.

Boeing ended Wednesday's session with losses of 3 percent, while the Dow dropped 1 percent.