NEW YORK ( TheStreet) -- Mitt Romney's best weapon for the China debate has also been his worst foe: investments. The Obama campaign on Monday highlighted the Republican presidential nominee's various former investments in Chinese companies like Youku ( YOKU) and Cnooc ( CEO), and linked them to intellectual property theft and piracy. It's a difficult connection for Romney to shake, but those investments also suggest a reality: China is investing in the United States, and those growth prospects could serve to pad the wallets of U.S. citizens and expand the U.S. economy. Instead of cheering the benefits of increased Chinese investments and expanded U.S.-China business partnerships, Romney has mostly criticized the trade partner and called President Barack Obama's China policy a failure. "He Romney fails to recognize just how huge and how important the trade and investment relationship is between the United States and China," said Donald Lewis, a Stanford Law School research fellow who teaches Chinese law and international economic law. "He's failing to recognize ... the very very substantial dealings that his own private-equity corporation Bain Capital has had with China on so many issues." Though Romney hasn't worked for Bain since he left the firm in February 1999 to work on organization of the 2002 Winter Olympic Games, according to a campaign official, the company has listed on its Web site several Chinese investments in recent years. Those investments included China Fire and Security Group (in 2011), ASIMCO Technologies (2010), Gymboree China (2011), JinSheng International (2007), Sinomedia Holding Limited (2006), SUNAC (2009) and Uniview (2011). Romney has refrained from touting his investment record with Bain, and he has generally sidestepped references to the private-equity firm -- this is largely because the Obama campaign has successfully pigeonholed Romney on Bain and equated his work there with pilfering middle-class jobs and shrewd profit-taking. To shed the image of a "China-basher" candidate who is only fixed on trashing the president's platform at all costs, and to re-form a perception that he has a fresh and constructive approach to handle the relationship, though, Romney could take the chance to discuss the advantage of encouraging investment affiliations.